1. Field of the Invention
This invention relates to a positive resist composition which responds to radiations such as ultraviolet ray, far ultraviolet rays including excimer laser and the like, electron beam, ion beam, X ray and the like.
2. Related Art
Recently, with a rise in the integration level of integrated circuits, formation of patterns of sub-micron order is required, and it is desired to provide a positive resist composition which is excellent in various properties such as a profile, a depth of focus and resolution. In particular, for the production of 16-64M DRAMs, it is required to resolve a pattern having a line width of 0.5 .mu.m or less with a good profile and a broad depth of focus.
In SPIE Vol. 1086, Advances in Resist Technology and Processing VI (1989)/Pages 363-373, there are mentioned positive resist compositions comprising a cresol/formaldehyde novolak resin and a triester obtained through a condensation reaction of naphtho-quinone-2-diazide-5-sulfonic acid with each of 2,3,4-trihydroxybenzophenone, 2,6-bis[(2-hydroxy-3,5-dimethylphenyl)methyl]-4-methylphenol and 2,6-bis[(4-hydroxy-3,5-dimethylphenyl)methyl]-4-methylphenol.
In Japanese Patent Application KOKAI No. 2-285351 (corresponds to U.S. Pat. No. 5,173,389), there is mentioned a positive photoresist composition comprising an alkali-soluble novolak resin and a photosensitive material obtained by reacting a polyhydroxy compound having at least one group represented by the following formula: ##STR2## wherein R.sup.1 and R.sup.2 each represent hydrogen or a straight chain or branched chain alkyl or alkoxy group having 1-4 carbon atoms, provided that R.sup.1 and R.sup.2 cannot simultaneously be hydrogen, and X represents a divalent organic group, with 1,2-naphthoquinone-5- (and/or -4-) sulfonyl chloride. Further, in Japanese Patent Application KOKAI No. 2-296249, there is mentioned a positive resist composition comprising an alkali-soluble phenolic resin and a photosensitive material containing a quinonediazide sulfonate of a compound represented by the following formula: ##STR3## wherein R.sup.1 to R.sup.5 each represent hydrogen, halogen, alkyl, alkenyl or alkoxy group having 1-4 carbon atoms or hydroxy group, provided that at least one of R.sup.1 to R.sup.5 is a group of the following formula: ##STR4## wherein R.sup.6 and R.sup.7 each represent halogen, alkyl group or alkenyl group and n is a number of 0, 1 or 2. Further, in Japanese Patent Application KOKAI No. 62-10646, there is mentioned a positive photoresist composition comprising an alkali-soluble phenolic resin and a photosensitive material containing a condensation product of a phenol compound represented by the following formula: ##STR5## wherein R.sup.1 to R.sup.3 each represent hydrogen or lower alkyl group, with o-quinonediazidesulfonyl chloride.
None of these compositions, however, have been able to resolve a pattern having a line width of 0.5 .mu.m or less with a broad depth of focus and a good profile.